1. Field of the Invention
The object of the invention is a method to be used in a suction device, such as a mechanical pipette, comprising a body and an associated end part with an open distal end directed away from the body for removably attaching a disposable tip enclosing a sample space for receiving a liquid sample, the end part of the suction device enclosing a cylinder space containing a reciprocatingly movable means for changing the volume of the cylindrical space for receiving a sample to the tip and removing it therefrom, for removing a barrier means adapted to the end part of the suction device and closing the opening in the end part. The object of the invention is also a suction device for employing the method.
2. Description of the Prior Art
In electronic as well as in mechanical suction devices, pipettes, barrier means are used in their end part to prevent liquids or reagents to be dispensed or molecules vaporizing from them from entering the inner parts of the pipette. These liquids or vaporized molecules in entering the inner parts of the pipette can contaminate the said inner parts and further in moving over from one sample to another can cause the contamination of the other sample. Samples and/or reagents can be valuable and in any case in the laboratory work cannot be accepted anything that deteriorates the reliability of the operation.
The barrier means are usually adapted to cover the opening in the end part of the suction device forming a gaseous passage between the cylindrical space in the end part of the suction device and a sample space of the disposable tip to be attached removably to the end part of the suction devices. The barrier means attach to the end part of the suction device, to the opening therein and/or to the cylindrical space so that they can easily be removed when desired.
The removal of the barrier means manually exposes the user of the suction device to samples or reagents which may be poisonous or dangerous.
To solve this problem, in the method according to the invention the barrier means are removed with the movement of the plunger, which is reciprocatingly movable in the cylindrical space of the suction device and which is intended for changing the volume of the cylindrical space. The said plunger is moved in the cylindrical space for taking samples or reagents into the disposable tip attached to the suction device, for dispensing and/or for removing them from the said tip. In these operations the plunger is moved between its two extreme positions, of which the first one with the plunger drawn into the cylinder corresponds the maximal suction, and of which the second one with the plunger coming to the vicinity of the opening in the end part of the suction device corresponds to the removal of the sample. For moving the plunger, the body of the suction device comprises operating means in association with the plunger. The suction device has preferably also means in association with the operating means for limiting the movement of the plunger in the cylindrical space.
The disposable tip attached to the suction device, onto the end of its end part, is removed in some suction devices with a sleeve movable on the end of the end part. The moving of the sleeve can take place as a separate operation directly manually or with separate means such as levers or bars. The sleeve can in some cases also be moved with means in association with the operating means of the said plunger or the means associated with the moving of the sleeve can be made in association with the operating means of the plunger or with means in association with it for removing the disposable tip by means of the sleeve.
The barrier means in the suction devices are removed from the suction device after the removal of the disposable tip when necessary, the barrier means are generally not always removed in connection of the removal of the disposable tip.
It is characteristic for the method according to the invention that the barrier means adapted to the end part of the suction device are removed by moving the plunger first in the direction of the opening in the end part of the suction device in contact with the barrier means and then by moving the plunger in the direction of the said opening for removing the barrier means from the end part of the suction device.
To prevent the unintentional or non-intended removal of the barrier means, the means for limiting the movement of the plunger in the cylindrical space are brought in one preferred embodiment of the method according to the invention in such a position in which the plunger cannot be moved into contact with the barrier means. When the barrier means are desired to be removed, the means limiting the movement of the plunger are brought in such a position that the plunger can be moved in contact with the barrier means and that in moving the plunger further in the direction of the opening in the end part, the movement of the plunger removes the barrier means from the end part of the suction device.
It is also characterizing to the suction device according to the invention that the suction device is provided with means which limit the movement of the plunger in the cylindrical space and which can be brought into at least one position in which the plunger can be brought in contact with the barrier means adapted to the end part of the suction device for removing the barrier means from the end part of the suction device.
In a preferred embodiment of the invention as means which limit the movement of the plunger and prevent the moving of the plunger into contact with the barrier means are used preferably means for removing the disposable tip such as e.g. the sleeve movable on the end of the end part and/or means associated with it, which means can be positioned with regard to the plunger and/or its operating means and/or means associated with them in a plurality of positions for limiting the movement of the plunger. When the user wants to remove the barrier means, the user selects such a position among the mutual positions between the plunger, its operating means and/or means associated with them, and the sleeve and/or means associated with it, in which the plunger can be moved into contact with the barrier means and in which position the plunger can further be moved for removing the barrier means.
In a preferred embodiment of the invention, the plunger is never brought directly into contact with the barrier means, but the plunger is provided with means, which in moving the plunger towards the opening in the end part of the suction device, can be brought into contact with the barrier means and which in continuing the movement of the plunger bring about the removal of the barrier means from the end part of the suction device. These means are in a preferred embodiment of the invention a telescopic extension of the plunger.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.